Project Summary/Abstract An estimated 2.3 billion people live at risk of infection by the Zika virus (ZIKV), a mosquito-borne flavivirus that causes microcephaly in newborns, as well as eye- and neurological defects, and Guillain-Barre syndrome in adults. Zika co-circulates in the same geographical region with the four serotypes of Dengue virus, which is of concern for both Dengue and Zika vaccine development. Antibodies that develop in response to Dengue can enhance Zika infection, and vice versa (Antibody-Dependent Enhancement, ADE). A recently discovered class of antibodies has been found to exhibit less ADE; these antibodies broadly and potently neutralize Zika and all four Dengue serotypes, and do so by binding to a quaternary epitope at the interface between adjacent E glycoprotein subunits on the viral envelope. This envelope dimer epitope (EDE) is a promising target for vaccine development. The goal of this exploratory R21 project is to discover glycopeptides that are good structural mimics of the EDE on ZIKV. Such molecules, when used as vaccine immunogens, should stimulate a broadly neutralizing antibody response that is protective against ZIKV, while avoiding ADE effects. The Krauss lab will use its directed evolution technology to scaffold the carbohydrate and peptide components of the EDE into arrangements that enable strong recognition by EDE antibodies, producing EDE mimics. Two further types of studies will then determine which among these glycopeptide ?hits? are best for future immunogenicity studies. The Sarathy and Barrett labs with determine whether selected glycopeptides compete with ZIKV for binding to the EDE antibodies, whereas the Wilson lab will determine structures of glycopeptide-antibody complexes to determine whether glycopeptides bind to the antibodies through ZIKV-like contacts.